Multi-axial connection system

ABSTRACT

In one embodiment of the present invention a system for connecting a fastener element (e.g., a pedicle screw) relative to a rod for the purposes of vertebral fixation is provided. The system may permit multi-axial movement between the fastener element and the rod. Further, the system may permit the angular relationship between the fastener element and the rod to be held in a desired orientation. For the purposes of describing and claiming the present invention, the term “rod” is intended to refer to any elongated structure. Such an elongated structure may be solid or hollow and may have any desired cross-section (e.g., circular, oval, square, rectangular). Further, for the purposes of describing and claiming the present invention, the term “interference fit” is intended to refer to physical contact between two or more components.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation in part of U.S. Application Ser. No.10/928,955, filed Aug. 27, 2004. This application also claims thebenefit of U.S. Provisional Application Ser. No. 60/665,173, filed Mar.25, 2005. Each of the aforementioned applications is incorporated hereinby reference in its entirely.

FIELD OF THE INVENTION

In one embodiment of the present invention a system for connecting afastener element (e.g., a pedicle screw) relative to a rod for thepurposes of vertebral fixation is provided. The system may permitmulti-axial movement between the fastener element and the rod. Further,the system may permit the angular relationship between the fastenerelement and the rod to be held in a desired orientation.

For the purposes of describing and claiming the present invention, theterm “rod” is intended to refer to any elongated structure. Such anelongated structure may be solid or hollow and may have any desiredcross-section (e.g., circular, oval, square, rectangular).

Further, for the purposes of describing and claiming the presentinvention, the term “interference fit” is intended to refer to physicalcontact between two or more components.

BACKGROUND OF THE INVENTION

Various systems for connecting fastener elements (e.g., pedicle screws)to elongated supports (e.g., rods) for the purposes of vertebralfixation have been proposed. Examples include the systems described inthe following U.S. Patents.

U.S. Pat. No. 5,466,237 relates to a variable locking stabilizer anchorseat and screw. More particularly, this patent relates to a boneinterface anchor provided for use with a stabilizer rod for the internalfixation of a spine. The anchor has a seat which accommodates thestabilizer rod and which receives a bone screw for the fixation of theseat to the bone. A compression member cooperates with the seat externalto the stabilizer rod and can be tightened to cause a compressive. forceon the stabilizer rod. The stabilizer rod bears on a rounded surface ofthe bone screw so as to cause a mating interface between the seat andthe bone screw. Subsequently, the position of the seat relative to thebone screw can be locked.

U.S. Pat. No. 5,474,555 relates to a spinal implant system. Moreparticularly, this patent relates to an apparatus for the internalfixation of the spine. The apparatus comprises an assembly having atleast two anchors and an elongated stabilizer. The anchors each havemeans to hold the anchor to the bone, and include receiving means whichreceive the stabilizer as well as securing means which cooperate withthe receiving means by means of the interaction of mating threads tocause the application of compression on the stabilizer into thereceiving means.

U.S. Pat. No. 5,669,911 relates to a polyaxial pedicle screw. Moreparticularly, this patent relates to a polyaxial orthopedic device foruse with rod implant apparatus. The device includes a screw having acurvate head, a locking collar disposed therearound, and a receivingmember having a linearly tapered socket in which the screw and thecollar are nested. The locking collar is slotted and tapered, and has asemi-spherical interior volume into which the screw head is initiallypolyaxially held. The receiving member has a transverse channel formedin it for receiving a rod, and an axial bore having a linearly taperedchamber in the bottom portion thereof. The collar is inserted down thebore from the top to seat in the chamber, and the screw is subsequentlyinserted up through the bottom of the bore and into the collar. Thelinear taper of the chamber provides a radially inward force on thelocking collar when the collar is forced downward therein. This radiallyinward force causes the locking collar to crush lock against the head ofthe screw, therein locking the two at the given angulation. It is theplacement of the rod in the transverse channel, against the top of thecollar, and the subsequent locking down of the rod in the channel whichprovides the downward force against the locking collar, which in turnlocks the screw in its given angulation.

U.S. Pat. No. 5,879,350 relates to a multi-axial bone screw assembly.More particularly, this patent relates to a multi-axial bone screwassembly including a bone screw having a partially spherical head. Thebone screw head is truncated at an upper surface in which a toolreceiving recess is defined. The assembly includes a receiver memberincluding a central bore that defines a tapered recess to receive acontracting collet carrying the head of the bone screw. The bore of thereceiver member also defines a channel communicating with the recess andconfigured to receive a spinal rod therein. A portion of the channel isthreaded to receive a set screw above the rod. The assembly alsoincludes a contracting collet disposed between the rod and the head ofthe bone screw. The collet defines a partially spherical recess toreceive the head of the bone screw, and includes deflectable fingersthat substantially surround the screw head. As the set screw istightened into the receiver member, the set screw compresses the rodagainst the collet, which presses the collet into the tapered recess ofthe receiver member, thereby deflecting the fingers of the colletagainst the bone screw head.

U.S. Pat. No. 6,063,090 relates to a device for connecting alongitudinal support to a pedicle screw. More particularly, this patentrelates to a device used to connect a longitudinal support to a pediclescrew by an accommodating head having a channel to accommodate thelongitudinal support, wherein it is possible to freely choose from ormix laterally open, top open or closed accommodating heads. A top openaccommodating head facilitates, for example, insertion of thelongitudinal support, whereas a lateral opening enables lateralcorrections. The pedicle screw and the accommodating head are connectedvia a conical collet chuck in the accommodating head and by a sphericalhead on the pedicle screw. The present invention allows engagement ofthe pedicle screw in the accommodating head after the pedicle screw hasbeen inserted into bone.

U.S. Pat. No. 6,582,436 relates to a device for connecting alongitudinal support to a bone anchor. More particularly, this patentrelates to a device for connecting a longitudinal support to a boneanchor having a rounded head. The device includes a body defining achamber for receiving the rounded head of the bone anchor and a firstchannel for receiving the longitudinal support. Further, a first sleeveis slidable over the body for compressing the chamber, a second sleeveis slidable over the body for biasing the longitudinal support againstthe first sleeve, and a fastener is operatively associated with the bodyfor biasing the second sleeve toward the first sleeve. The forcesexerted on the second sleeve by the fastener are transferred to thefirst sleeve in a plane perpendicular to the central axis. Preferably,the longitudinal support contacts the first sleeve at first and secondcontact points or zones and one of the sleeves includes at least oneextended portion for contacting the other sleeve at least one additionalcontact point or zone.

U.S. Pat. No. 6,660,004 relates to a multi-axial bone screw assembly.More particularly, this patent relates to a bottom-loading multi-axialbone anchor apparatus. The apparatus includes a receiver member, a crownmember, a bone anchor and a retaining member. The receiver memberdefines an upper opening and a lower opening, which may form part of thesame opening, a channel, and a groove. The crown member and bone anchorare loaded into the lower opening of the receiver member, and theretaining member fits around the bone anchor and into the groove in thereceiver member. The bone anchor is capable of multi-axial positioningwith respect to the receiver member. An elongated member is placed inthe channel of the receiver member, contacting the crown member, and acompression member is applied via the upper opening. The compressionmember presses down on the elongated member, which presses down on thecrown member and locks the bone anchor between the crown member and theretaining member.

U.S. Pat. No. 6,740,086 relates to a screw and rod fixation assembly anddevice. More particularly, this patent relates to a screw and rodfixation assembly for fixing a screw and, optionally, a rod. The screwand rod fixation assembly includes a screw, fixing mechanism, asubstantially annular ring, rod seating mechanism, and lockingmechanism. The present invention also provides for a fixing mechanismfor fixing a screw, wherein the fixing mechanism further includes aninner surface wall having a gripping portion and a non-gripping portion.Further, the present invention provides for a substantially annular ringfor guiding and providing mechanical and frictional force to a screwhead. Additionally, the present invention provides for a rod seatingmechanism operatively engaged to the screw head and including at leastone flexible portion capable of being compressed against a portion of arod therein. Finally, the present invention provides for a lockingmechanism for engaging the rod and the rod seating mechanism. Thelocking mechanism includes a deflecting mechanism for deflecting the atleast one flexible portion of the rod seating mechanism against andaround the rod as the locking mechanism further engages the at least oneflexible portion of the rod seating mechanism.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an exploded perspective view of a fastener assemblyaccording to an embodiment of the present invention;

FIG. 2 shows a cross-sectional view of a partially assembled fastenerassembly according to the embodiment of FIG. 1 (for clarity, this FIG.does not include the rod or compression member of FIG. 1);

FIG. 3 shows an exploded perspective view of a fastener assemblyaccording to another embodiment of the present invention:

FIG. 4 shows a cross-sectional view of a partially assembled fastenerassembly according to the embodiment of FIG. 3 (for clarity, this FIG.does not include the rod or compression member of FIG. 3);

FIG. 5 shows a side view of a fastener assembly according to anotherembodiment of the present invention;

FIG. 6 shows a side view of a fastener assembly according to anotherembodiment of the present invention;

FIG. 7 shows a side view of a fastener according to an embodiment of thepresent invention;

FIGS. 8A and 8B show, respectively, an elevational view and aperspective view of an offset design according to an embodiment of thepresent invention;

FIGS. 9A and 9B show, respectively, an elevational view and aperspective view of an offset design according to an embodiment of thepresent invention; and

FIGS. 10A and 10B show, respectively, an elevational view and aperspective view of an offset design according to an embodiment of thepresent invention.

Among those benefits and improvements that have been disclosed, otherobjects and advantages of this invention will become apparent from thefollowing description taken in conjunction with the accompanyingfigures. The figures constitute a part of this specification and includeillustrative embodiments of the present invention and illustrate variousobjects and features thereof.

DETAILED DESCRIPTION OF THE INVENTION

Detailed embodiments of the present invention are disclosed herein;however, it is to be understood that the disclosed embodiments aremerely illustrative of the invention that may be embodied in variousforms. In addition, each of the examples given in connection with thevarious embodiments of the invention are intended to be illustrative,and not restrictive. Further, the figures are not necessarily to scale,some features may be exaggerated to show details of particularcomponents. Therefore, specific structural and functional detailsdisclosed herein are not to be interpreted as limiting, but merely as arepresentative basis for teaching one skilled in the art to variouslyemploy the present invention.

Referring now to FIGS. 1 and 2, a first embodiment of the presentinvention is shown. As seen in these FIGS., Fastener Assembly 100 may beused in connection with mounting Rod 101 relative to a spine of apatient (of course, one or more such Fastener Assemblies may be usedwith one or more Rods). More particularly, Fastener Assembly 100 mayinclude Fastener 103 having Head 103A at a first end and Bone ConnectionElement 103B at a second end (Bone Connection Element 103B may beadapted for attachment on, in and/or to the spine). Further, Head 103Amay include at least one Deformation Element 103C thereon.

In one example (which example is intended to be illustrative and notrestrictive), at least a portion of Head 103A may be spherical. Inanother example (which example is intended to be illustrative and notrestrictive), Fastener 103 may be a bone screw and Bone ConnectionElement 103B may comprise threads. In another example (which example isintended to be illustrative and not restrictive), Fastener 103 may be acannulated bone screw (see Cannulation 103D of FIG. 2). In anotherexample (which example is intended to be illustrative and notrestrictive), Deformation Element 103C may substantially surroundCannulation 103D (e.g., where Cannulation 103D exits Head 103A). Inanother example (which example is intended to be illustrative and notrestrictive), Deformation Element 103C may be a substantially circularring protruding from Head 103A. In another example (which example isintended to be illustrative and not restrictive), Deformation Element103C (and/or any other portion of Fastener 103 (e.g., Head 103A or theentire Fastener 103)) may include a material which is: (a) softer than amaterial from which Rod 101 is formed; (b) harder than a material fromwhich Rod 101 is formed; or (c) of essentially the same hardness as amaterial from which Rod 101 is formed (e.g., the same material fromwhich Rod 101 is formed).

Still referring to FIGS. 1 and 2, it is seen that Fastener Assembly 100may include Body 105. Body 105 may have a first end and a second end,wherein Rod Receiving Channel 105A for receiving Rod 101 is disposedadjacent the first end of Body 105 and Fastener Head Receiving Chamber105B is disposed adjacent the second end of Body 105 (as seen in theseFIGS., Fastener Head Receiving Chamber 105B may be tapered towards thesecond end of Body 105 and Rod Receiving Channel 105A and Fastener HeadReceiving Chamber 105B may be operatively connected (e.g., a hole inBody 105 may connect Rod Receiving Channel 105A and Fastener HeadReceiving Chamber 105B)).

Further, Fastener Assembly 100 may include Retention Ring 107. ThisRetention Ring 107 may be sized to fit at least partially around Head103A when Head 103A is disposed within Fastener Head Receiving Chamber105B. In one example (which example is intended to be illustrative andnot restrictive), Retention Ring 107 may be, as shown in the Figs., of a“split-ring” design.

Further still, Compression Element 109 may cooperate with Body 105 topush Rod 101, when Rod 101 is disposed within Rod Receiving Channel105A, into contact with at least part of Deformation Element 103C. Suchcontact between Rod 101 and Deformation Element 103C will deformDeformation Element 103C while pressing Head 103A towards the taperedend (i.e., narrower end) of Fastener Head Receiving Chamber 105B. Thisaction will serve to fix the angular relationship of Fastener 103relative to Rod 101.

More particularly, the angular relationship of Fastener 103 relative toRod 101 may be fixed at least in part due to: (a) an interference fit(caused by radial compression) between at least a portion of an outsidesurface of Head 103A and at least a portion of an inside surface ofRetention Ring 107; (b) an interference fit (caused by radialcompression) between at least a portion of an outside surface ofRetention Ring 107 and at least a portion of an inside surface ofFastener Head Receiving Chamber 105B; and/or (c) an interference fitbetween at least a portion of an outside surface of Rod 101 andDeformation Element 103C.

In one example (which example is intended to be illustrative and notrestrictive), Compression Element 109 may have threads which cooperatewith complementary threads of Body 105. In another example (whichexample is intended to be illustrative and not restrictive), CompressionElement 109 may have external threads which cooperate with complementaryinternal threads of Body 105 (e.g., Compression Element 109 may be a setscrew). In another example (which example is intended to be illustrativeand not restrictive), Compression Element 109 may have internal threadswhich cooperate with complementary external threads of Body 105 (e.g.,Compression Element 109 may be a nut). In another example (which exampleis intended to be illustrative and not restrictive), Compression Element109 may have one or more indentations, protrusions and/or drive facesfor receiving torque from a drive tool (see, e.g., the female hexfeature of FIG. 1).

Reference will now be made to the elements shown in FIGS. 1 and 2 inconnection with the description of an example installation procedure.Such an example installation procedure is applicable to this embodimentof the fastener assembly of the present invention and, of course, isintended to be illustrative and not restrictive.

More particularly, a guide wire may first be attached to a pedicle ofthe spine. The free end of the guide wire may then be passed throughFastener 103 (via Cannulation 103D). Fastener 103 (e.g., a pediclescrew) may then be inserted (e.g., screwed into) the pedicle of thespine. Of note, such a pedicle screw may be self-tapping into a holebored into the pedicle or the hole bored into the pedicle may bepre-tapped. Of further note, such a pedicle screw may be driven intobone with any desired tool (e.g., a hand or power driver applying torquethrough Rod Receiving Channel 105A and Fastener Head Receiving Chamber105B).

In one example (which example is intended to be illustrative and notrestrictive), such a pedicle screw may be driven into bone with a torqueapplying tool that engages one or more indentations, protrusions and/ordrive faces on Head 103A (see, e.g., the four scallops of Head 103A inFIG. 1).

In one example (which example is intended to be illustrative and notrestrictive), Fastener 103 may be driven into bone by itself. Next, abody/retention ring assembly (e.g., including Body 105 having RetentionRing 107 already disposed within Fastener Head Receiving Chamber 105B)may be placed (or “snapped”) onto Fastener 103.

In this regard, as Body 105 is subsequently pushed onto Head 103A,Retention Ring 107 is pushed against the back wall of Fastener HeadReceiving Chamber 105B (see 105C of FIG. 2) and Retention Ring 107 isfree to expand outward enabling Head 103A to pass through. Once Head103A pushes through the bottom of Retention Ring 107, Head 103A remainscaptured (since Retention Ring 107 would have no room to expand as itwas pulled forward by Head 103A towards the tapered (i.e., narrowed) endof Fastener Head Receiving Chamber 105B.

Next, Rod 101 may be placed in Rod Receiving Channel 105A (with Rod 101coming into contact with Deformation Element 103C.

Finally, as Compression Element 109 (e.g., a set screw) is threaded intoBody 105, Compression Element 109 clamps the components in a setposition (that is, Compression Element 109 pushes Rod 101 againstDeformation Element 103C (and, depending upon the size and shape of Rod101, Deformation Element 103C and Head 103A, against a portion of Head103A)). Of note, during this clamping process Deformation Element 103Cis deformed (e.g., to form a surface complementary to the portion of Rod101 causing the deformation) and the result is improved locking (e.g.,of the angular relationship between Rod 101 and Fastener 103). Offurther note, it is believed that Deformation Element 103C isparticularly useful in enabling secure locking of canulated fasteners,such as cannulated pedicle screws (it is believed that a cannulation(without the use of a deformation element according to the presentinvention) may tend to compromise the ability to lock the multi-axialadjustability against the rod (e.g., due to a circular cross-section ofthe rod)).

In another example (which example is intended to be illustrative and notrestrictive), rather than driving Fastener 103 into bone by itself andthen placing a body/retention ring assembly thereon, Fastener 103 may becaptured within body/retention ring assembly as discussed above and thenthe entire body/retention ring/fastener assembly may be attached to thebone (e.g., by using a driving tool such as a hand or power driver todrive the pedicle screw through the hole provided in Body 105 betweenRod Receiving Channel 105A and Fastener Head Receiving Chamber 105B).

Referring now to FIGS. 3 and 4, another embodiment of the presentinvention is shown. This embodiment is similar to the embodiment shownin FIGS. 1 and 2 and, in this regard, the same elements will beidentified by the same reference numerals (such similar elements willnot be described again in detail). Of note, the main difference betweenthe embodiment of these FIGS. 3 and 4 and the embodiment of FIGS. 1 and2 is that in this embodiment Fastener Assembly 200 does not utilizeRetention Ring 107.

More particularly, Fastener Assembly 200 may again be used in connectionwith mounting Rod 101 relative to a spine of a patient (of course, oneor more such Fastener Assemblies may be used with one or more Rods).Further, Fastener Assembly 200 may include Fastener 103 (having Head103A, Bone Connection Element 103B and at least one Deformation Element103C).

Still referring to FIGS. 3 and 4, it is seen that Fastener Assembly 200may further include Body 105′ (Body 105′ may have a first end and asecond end, wherein Rod Receiving Channel 105A′ for receiving Rod 101 isdisposed adjacent the first end of Body 105′ and Fastener Head ReceivingChamber 105B′ is disposed adjacent the second end of Body 105′). As seenin these FIGS., Fastener Head Receiving Chamber 105B′ may be taperedtowards the second end of Body 105′ and a hole may be disposed throughBody 105′ to connect Rod Receiving Channel 105A′ and Fastener HeadReceiving Chamber 105B′.

Of note, the tapered (i.e., narrow) end of Fastener Head ReceivingChamber 105B′ may be made sufficiently small so as to prohibit Head 103Afrom passing therethrough (while Rod Receiving Channel 105A′ and thehole in Body 105′ connecting Rod Receiving Channel 105A′ to FastenerHead Receiving Chamber 105B′ may be made sufficiently large so as toallow Head 103A to pass therethrough).

In this regard, Fastener Assembly 200 may be installed by insertingFastener 103 through Body 105′ such that Head 103A comes to rest inFastener Head Receiving Chamber 105B′ (see FIG. 4). Fastener 103 maythen be inserted (e.g., into the pedicle of the spine) as discussedabove (e.g., a guide wire may be used to guide Fastener 103 and either aself-tapping bone screw may be driven into a hole in the bone or apre-tapped hole in the bone may be provided).

Finally, Compression Element 109 may cooperate with Body 105′ to pushRod 101, when Rod 101 is disposed within Rod Receiving Channel 105A′,into contact with at least part of Deformation Element 103C to deformDeformation Element 103C while pressing Head 103A towards the taperedend (i.e., narrower end) of Fastener Head Receiving Chamber 105B. Thisaction will fix the angular relationship of Fastener 103 relative to Rod101 (the angular relationship of Fastener 103 relative to Rod 101 may befixed at least in part due to: (a) an interference fit (caused by radialcompression) between at least a portion of an outside surface of Head103A and at least a portion of an inside surface of Fastener HeadReceiving Chamber 105B′; and/or (b) an interference fit between at leasta portion of an outside surface of Rod 101 and Deformation Element 103C.

Referring now to FIGS. 5 and 6, two other embodiments of a fastenerassembly body are shown. In this regard, it is noted that Body 105 ofFIGS. 1 and 2 has an upward facing Rod Receiving Channel 105A forreceiving Rod 101. Likewise, Body 105′ of FIGS. 3 and 4 has an upwardfacing Rod Receiving Channel 105A′ for receiving Rod 101. In contrast,it is seen in FIG. 5 that Body 500 includes a sideward facing RodReceiving Channel 501 for receiving Rod 101 (Rod 101, Fastener 103,Compression Element 109 and Retention Ring 107 are shown in phantom andare essentially the same elements as described in detail above).Further, it is seen in FIG. 6 that Body 600 includes a “tunnel-type” RodReceiving Channel 601 for receiving Rod 101 (Rod 101, Fastener 103,Compression Element 109 and Retention Ring 107 are shown in phantom andare essentially the same elements as described in detail above). Ofnote, the embodiments of these FIGS. 5 and 6 may operate as discussedabove (e.g., the body may include a tapered chamber for facilitating aninterference fit between the components disposed therein).

Referring now to FIG. 7, another embodiment of a fastener for use withthe present invention is shown. Of note, Fastener 700 is depicted hereas a bone screw, although other types of bone attaching mechanisms may,of course, be utilized (e.g., a shaft having a hook on the end). In anycase, it is seen that in this embodiment Undercut 701 is provided(Undercut 701 may be formed, for example, by a flattening of the bottomof the head of the bone screw (see 701A) and/or by a narrowing of aportion of the shaft of the bone screw (see 701B)). By using suchUndercut 701, Fastener 700 may provide increased clearance in the areawhere Fastener 700 extends from the body of the fastener assembly(wherein such increased clearance may translate into an increase in amaximum angle that Fastener 700 may obtain in relation to the fastenerbody and/or the rod.

Referring now to FIGS. 8A and 8B, it is seen that these FIGS. show,respectively an elevational view and a perspective view of an offsetdesign according to an embodiment of the present invention. In theexample of these FIGS. 8A and 8B (which example is intended to beillustrative and not restrictive), Body 805 includes a lateral offset(e.g., an 8mm lateral offset) between Fastener Head Receiving Chamber805B and Rod Receiving Channel 805A. Further, Rod Receiving Channel 805Ais angled (e.g., 50 degrees) from vertical (and from a vertical axisdisposed through Fastener Head Receiving Chamber 805B). Of note, suchoffset design may be used in a manner similar to that described withrespect to the non-offset designs (e.g., Body 105) disclosed herein (forexample, a first compression element, such as a set screw (not shown inthese FIGS. 8A and 8B), may be used to fix the rod (not shown in theseFIGS. 8A and 8B) relative to the body and a second compression element,such as a set screw (not shown in these FIGS. 8A and 8B), may be used tofix the bone screw (not shown in these FIGS. 8A and 8B) relative to thebody).

Referring now to FIGS. 9A and 9B, it is seen that these FIGS. show,respectively an elevational view and a perspective view of an offsetdesign according to an embodiment of the present invention. In theexample of these FIGS. 9A and 9B (which example is intended to beillustrative and not restrictive), Body 905 includes a lateral offset(e.g., an 11 mm lateral offset) between Fastener Head Receiving Chamber905B and Rod Receiving Channel 905A. Further, Rod Receiving Channel 905Ais angled (e.g., 25 degrees) from vertical (and from a vertical axisdisposed through Fastener Head Receiving Chamber 905B). Of note, suchoffset design may be used in a manner similar to that described withrespect to the non-offset designs (e.g., Body 105) disclosed herein (forexample, a first compression element, such as a set screw (not shown inthese FIGS. 9A and 9B), may be used to fix the rod (not shown in theseFIGS. 9A and 9B) relative to the body and a second compression element,such as a set screw (not shown in these FIGS. 9A and 9B), may be used tofix the bone screw (not shown in these FIGS. 9A and 9B) relative to thebody).

Referring now to FIGS. 10A and 10B, it is seen that these FIGS. show,respectively an elevational view and a perspective view of an offsetdesign according to an embodiment of the present invention. In theexample of these FIGS. 10A and 10B (which example is intended to beillustrative and not restrictive), Body 1005 includes a lateral offset(e.g., a 14 mm lateral offset) between Fastener Head Receiving Chamber1005B and Rod Receiving Channel 1005A. Further, Rod Receiving Channel1005A is angled (e.g., 15 degrees) from vertical (and from a verticalaxis disposed through Fastener Head Receiving Chamber 1005B). Of note,such offset design may be used in a manner similar to that describedwith respect to the non-offset designs (e.g., Body 105) disclosed herein(for example, a first compression element, such as a set screw (notshown in these FIGS. 10A and 10B), may be used to fix the rod (not shownin these FIGS. 10A and 10B) relative to the body and a secondcompression element, such as a set screw (not shown in these FIGS. 10Aand 10B), may be used to fix the bone screw (not shown in these FIGS.10A and 10B) relative to the body).

Of note, the offset designs may or may not utilize a screw with adeformation element. For example, a screw with a deformation element maybe utilized such that the compression element interfacing with the screwpresses down on and deforms the deformation element. In another example,a screw with a deformation element may be utilized such that thecompression element interfacing with the screw presses down on the screwhead itself but the compression element includes a cavity adjacent thescrew head and aligned with the deformation element such that thedeformation element does not deform. In another example, the screw headmay not have a deformation element at all.

Of further note, the offset designs may ease assembly of the fixationsystem (e.g., by providing a surgeon laterally offset/angled optionswhen connecting the spinal rod(s)).

In another embodiment (applicable to both the offset and non-offsetdesigns), the body may (before being fixed relative to the bone screw):(a) be circumferentially rotatable on the head of the bone screw aroundthe longitudinal axis of the bone screw; and/or (b) have a desireddegree of angular freedom (e.g., 26 degrees from the longitudinal axisof the bone screw (or 52 degrees from one side to the other).

While a number of embodiments of the present invention have beendescribed, it is understood that these embodiments are illustrativeonly, and not restrictive, and that many modifications may becomeapparent to those of ordinary skill in the art. For example, the presentinvention may be placed at any desired level of the spine. Further, thepresent invention may be used in conjunction with a posterior spinal rodimplantation. Further still, the controllable angulation provided by thepresent invention may be in any desired number of planes. Further still,the rod may be fixed axially and rotationally. Further still, anyelement described herein may be provided in any desired size (e.g., anyelement described herein may be provided in any desired custom size orany element described herein may be provided in any desired sizeselected from a “family” of sizes, such as small, medium, large. To givea more specific example (which example is intended to be illustrativeand not restrictive), a bone screw may be provided in a desired threadpitch, thread outer diameter, shaft outer diameter, shaft outer diameterto thread outer diameter ratio and/or length and a body element may beprovided in any desired inner diameter, outer diameter, lateral offset,angle and/or length. Further still, the compression element may have a“break-off” feature for separating from the installed portion of thecompression element when a desired amount of torque has been applied.Further still, one or more of the components of the fastener assemblymay be made from any of the following materials: (a) any biocompatiblematerial (which biocompatible material may be treated to permit boneingrowth or prohibit bone ingrowth—depending upon the desire of thesurgeon); (b) a plastic; (c) a fiber; (d) a polymer; (e) a metal (a puremetal such as titanium and/or an alloy such as Ti—Al—Nb, Ti-6Al-4V,stainless steel); (f) any combination thereof. Further still, use of theguide wire for guiding the fastener via the cannulation may be usefulduring a minimally invasive procedure, for example. Further still, thebone screw may be adapted for placement in cancellous bone. Furtherstill, rather than a thread, the fastener may employ a hook forattachment to bone. Further still, an outer surface of the head of thefastener, an outer surface of the rod, an outer surface of the retentionring, an inner surface of the retention ring and/or an inner surface ofthe body (e.g., at any interface area between the aforementionedcomponents) may have one or more features for increasing friction at theinterface. For example, any of the aforementioned components may have: aroughened or treated surface (e.g., via sandblasting or knurling), athreaded surface, a grooved surface, a ridged surface, a surface withprotrusions, and/or a surface with indentations. Further still, thedeformation element may deform in dependence upon: (a) the materialutilized for the deformation element; (b) the material utilized for therod; (c) the material utilized for the compression element; (d) ageometry of the rod in the area where the rod contacts the deformationelement; (e) a geometry of the deformation element; (f) a geometry ofthe compression element where the compression element contacts thedeformation element; (g) a direction of a load applied to thedeformation element by the rod; (h) a direction of a load applied to thedeformation element by the compression element; (i) a magnitude of aload applied to the deformation element by the rod; and/or (j) amagnitude of a load applied to the deformation element by thecompression element. Further still, a minimum of two fastener assembliesfor each rod may be used (e.g., for stabilization purposes). Furtherstill, any type and number of features may be utilized for interfacingwith an installation tool (see, e.g., the holes disposed on the outersurface of the body of the device—these holes may mate withcorresponding retractable pins of an installation tool). Further still,any steps described herein may be carried out in any desired order (andany additional desired steps may be added and/or any desired stepsdeleted).

1. A spinal fixation system, comprising: at least one rod; at least onescrew having a head at a first end, wherein the screw has a longitudinalaxis associated therewith; and at least one body to which the rod andthe screw are attached; wherein the body comprises a screw headreceiving chamber which receives the screw along the longitudinal axisof the screw and which contains the head of the screw; wherein the bodycomprises a rod receiving channel which receives the rod; wherein thescrew head receiving chamber and the rod receiving channel are laterallyoffset from one another; and wherein the rod receiving channel is angledrelative to the screw head receiving chamber.
 2. The spinal fixationsystem of claim 1, wherein the screw head receiving chamber and the rodreceiving channel are laterally offset from one another by a distance ofbetween about 8 mm to about 14 mm.
 3. The spinal fixation system ofclaim 2, wherein the screw head receiving chamber and the rod receivingchannel are laterally offset from one another by a distance of about 8mm.
 4. The spinal fixation system of claim 2, wherein the screw headreceiving chamber and the rod receiving channel are laterally offsetfrom one another by a distance of about 11 mm.
 5. The spinal fixationsystem of claim 2, wherein the screw head receiving chamber and the rodreceiving channel are laterally offset from one another by a distance ofabout 14 mm.
 6. The spinal fixation system of claim I, wherein the screwhead receiving chamber is tapered.
 7. The spinal fixation system ofclaim 6, wherein the screw head receiving chamber is tapered along ascrew head receiving chamber axis which is substantially parallel to thelongitudinal axis of the screw received therein.
 8. The spinal fixationsystem of claim 1, further comprising a compression element whichcooperates with the body to attach the rod to the body.
 9. The spinalfixation system of claim 8, wherein the compression element comprises aset screw which interfaces with threads associated with the rodreceiving channel.
 10. The spinal fixation system of claim 1, furthercomprising a compression element which cooperates with the body toattach the screw to the body.
 11. The spinal fixation system of claim10, wherein the compression element comprises a set screw whichinterfaces with threads associated with the screw head receivingchamber.
 12. The spinal fixation system of claim 11, wherein thecompression element presses the head of the screw towards the taperedend of the screw head receiving chamber to fix an angular relationshipof the screw relative to the body and to the rod received in the rodreceiving channel.
 13. The spinal fixation system of claim 12, whereinthe angular relationship of the screw relative to the body and to therod received in the rod receiving channel is fixed at least in part dueto: an interference fit between at least a portion of an outside surfaceof the head of the screw and at least a portion of an inside surface ofthe screw head receiving chamber; and (b) an interference fit between atleast a portion of an outside surface of the head of the screw and thecompression element.
 14. The spinal fixation system of claim 12, furthercomprising a retention ring sized to fit at least partially around thehead of the screw when the head of the screw is disposed within thescrew head receiving chamber.
 15. The spinal fixation system of claim14, wherein the angular relationship of the screw relative to the bodyand to the rod received in the rod receiving channel is fixed at leastin part due to: (a) an interference fit between at least a portion of anoutside surface of the head of the screw and at least a portion of aninside surface of the retention ring; (b) an interference fit between atleast a portion of an outside surface of the retention ring and at leasta portion of an inside surface of the screw head receiving chamber; and(c) an interference fit between at least a portion of an outside surfaceof the head of the screw and the compression element.
 16. The spinalfixation system of claim 1, wherein the screw is a bone screw.
 17. Thespinal fixation system of claim 16, wherein the bone screw is configuredto be screwed into a pedicle portion of a spine.
 18. The spinal fixationsystem of claim 16, wherein the bone screw is a cannulated bone screw.19. The spinal fixation system of claim 1, wherein the rod receivingchannel is configured to allow a tool to be inserted therethrough toapply torque to the screw.
 20. The spinal fixation system of claim 19,wherein the head of the screw includes at least one torque receivingfeature for receiving torque from the tool.
 21. The spinal fixationsystem of claim 20, wherein the torque receiving feature is selectedfrom the group including: (a) at least one indentation; (b) at least oneprotrusion; and (c) at least one drive face.
 22. The spinal fixationsystem of claim 1, wherein the rod has a substantially circular crosssection.
 23. The spinal fixation system of claim 1, wherein the head ofthe screw is at least partially spherical.
 24. A spinal fixation system,comprising: at least one rod; at least one bone screw having a head at afirst end, wherein the bone screw has a longitudinal axis associatedtherewith; at least one body to which the rod and the bone screw areattached; a first compression element which cooperates with the body toattach the rod to the body; and a second compression element whichcooperates with the body to attach the bone screw to the body; whereinthe body comprises a screw head receiving chamber which receives thebone screw along the longitudinal axis of the bone screw and whichcontains the head of the bone screw, wherein the screw head receivingchamber is tapered along a screw head receiving chamber axis which issubstantially parallel to the longitudinal axis of the bone screwreceived therein; wherein the body comprises a rod receiving channelwhich receives the rod; wherein the first compression element comprisesa set screw which interfaces with threads associated with the rodreceiving channel; wherein the second compression element comprises aset screw which interfaces with threads associated with the screw headreceiving chamber and wherein the second compression element presses thehead of the bone screw towards the tapered end of the screw headreceiving chamber to fix an angular relationship of the bone screwrelative to the body and to the rod received in the rod receivingchannel; wherein the screw head receiving chamber and the rod receivingchannel are laterally offset from one another; wherein the rod receivingchannel is angled relative to the screw head receiving chamber; whereinthe screw head receiving chamber and the rod receiving channel arelaterally offset from one another by a distance of between about 8 mm toabout 14 mm; wherein the bone screw is configured to be screwed into apedicle portion of a spine; and wherein the head of the bone screw is atleast partially spherical.